A study of the relationship between the liver damage and the metabolic formation of free radicals from halogenated hydrocarbons by the liver mixed-function oxidase system would be undertaken. In addition, the studies on the effects of induction of the mixed-function oxidase system and free radical scavengers on the above relationship is proposed. Substances to be investigated include halogenated hydrocarbons which have been shown to be hapatotoxic, carcinogenic or both. The extent of correlation of free radical formation from these compounds by the mixed-function oxidase system of the liver with the toxic effect of the halogenated hydrocarbons will be investigated. Subtances to be studied include trichloroethylene, 1,1,1-trichloroethane, vinyl chloride, and the Freon compouond (Freon II) trichlorofluoromethan. Preliminary studies by the applicants indicate that the metabolism of the halogenated hydrocarbons tested thus far show a common property; that is, the formation of a free radical when metabolized by the mixed-function oxidase system of liver microsome. Reconstituted mixed-function oxidase systems of purified cy tochrom P-450 and P-450 reductase show that one specific cytochrome P-450 and P-450 redyctase show that one specific cytochrome P-450 (52,000 MW) converts CC14 to a CC13 radical. This cytochrome P-450 is preferentially damaged when CC14 is given in vivo. We will investigate which cytochrome P-450 species are active in generating free radical products during halogenated hydrocarbon metabolism. Also, we propose to determine if there is a correlation between radical formation and damage to the liver microsomal ATP-dependent calcium (pump) uptake function, both in vivo and in vitro. Using ESR spin-trapping techniques combined with computer simulation, we have developed a method for decting and identifying free radical intermediates formed from halogenated hydrocarbons by the mixed-function oxidase system. By combining this method with a study of the reaction of these radical intermediates with subcellular components, and the capacity of antioxidant free radical scavenging agents, to prevent such reactions, both the nature of the toxicity and a practical means for preventing such toxicity may emerge from these studies.